1. Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus of allocating a radio resource in a frequency division duplex (FDD) frame capable of effectively supporting a half-duplex FDD (H-FDD) type user equipment.
2. Related Art
The institute of electrical and electronics engineers (IEEE) 802.16 standard provides a technique and protocol for supporting broadband wireless access. The standardization had been conducted since 1999 until the IEEE 802.16-2001 was approved in 2001. The IEEE 802.16-2001 is based on a physical layer of a single carrier (SC) called ‘WirelessMAN-SC’. The IEEE 802.16a standard was approved in 2003. In the IEEE 802.16a standard, ‘WirelessMAN-OFDM’ and ‘WirelessMAN-OFDMA’ are further added to the physical layer in addition to the ‘WirelessMAN-SC’. After completion of the IEEE 802.16a standard, the revised IEEE 802.16-2004 standard was approved in 2004. To correct bugs and errors of the IEEE 802.16-2004 standard, the IEEE 802.16-2004/Cor1 (hereinafter, IEEE 802.16e) was completed in 2005 in a format of ‘corrigendum’.
Communication between a base station (BS) and a user equipment (UE) includes downlink (DL) transmission from the BS to the UE and uplink (UL) transmission from the UE to the BS. A system profile based on the existing IEEE 802.16e supports a time division duplex (TDD) scheme in which DL transmission and UL transmission are divided in a time domain. In the TDD scheme, UL transmission and DL transmission are performed at different times by using the same frequency band. The TDD scheme has an advantage in that frequency selective scheduling is simply performed since a UL channel characteristic and a DL channel characteristic are reciprocal.
At present, there is ongoing standardization effort for the IEEE 802.16m standard which is a new technical standard based on the IEEE 802.16e. The IEEE 802.16e system considers not only a frequency division duplex (FDD) scheme but also a half-duplex FDD (H-FDD) scheme. In the FDD scheme, DL transmission and UL transmission are simultaneously performed by using different frequency bands. In the H-FDD scheme, DL transmission and UL transmission are performed at different times by using different frequency bands. That is, the H-FDD scheme does not perform DL transmission and UL transmission simultaneously, and a DL radio resource and a UL radio resource are not allocated to a UE using the H-FDD scheme in the same time domain.
An evolution system evolved from a legacy system has to be designed to operate by incorporating the legacy system, which is referred to as backward compatibility. The evolution system employing the FDD scheme and the H-FDD scheme is evolved from the legacy system supporting the TDD scheme and has to effectively support the FDD scheme and the H-FDD scheme while satisfying backward compatibility. However, a frame structure capable of effectively supporting backward compatibility of the H-FDD scheme while satisfying backward compatibility with the legacy system has not been clearly proposed yet.
In addition, heterogeneous wireless communication systems using different communication schemes may share a frequency band. When the heterogeneous wireless communication systems use the frequency band in an FDD-type frame by dividing the frequency band according to time division multiplexing (TDM), a frame structure needs to be designed by considering a UE that uses the H-FDD scheme. However, the frame structure capable of effectively supporting the H-FDD scheme and the heterogeneous wireless communication systems has not been clearly introduced yet.